Human influenza hemagglutinin (HA) is a surface glycoprotein required for the infectivity of the human virus. The HA tag is derived from the HA-molecule corresponding to amino acids 98-106 has been extensively used as a general epitope tag in expression vectors. Many recombinant proteins have been engineered to express the HA tag, which does not appear to interfere with the bioactivity or the biodistribution of the recombinant protein. This tag facilitates the detection, isolation, and purification of the proteins.

TSC22 domain family, member 1 (TSC22D1) is one of the TGF-beta-stimulated clone-22 (TSC-22). TSC-22 was reported to be a differentiation-inducing factor which negatively regulates the growth of salivary gland cancer cells. TSC22D1, which encodes transforming growth factor beta-stimulated clone 22 (TSC-22), is thought to be a tumor suppressor because its expression is lost in many glioblastoma, salivary gland, and prostate cancers. TSC-22 is the founding member of the TSC-22/DIP/Bun family of leucine zipper transcription factors. TSC-22 may play an important role in maintaining the differentiated phenotype in salivary gland tumors, and may be a possible target of leukemia therapy. TSC22D1 forms homodimers via its conserved leucine zipper domain and heterodimerizes with TSC22D4. TSC22D1 has transcriptional repressor activity.